Compressed gas engine

ABSTRACT

A compressed gas engine is provided. The compressed gas engine may include a first crankshaft, a first set of piston assemblies, a second set of piston assemblies, and a first valve assembly. The first set of piston assemblies may be coupled to the first crankshaft and comprise a first piston assembly having a first diameter and a second piston assembly having a second diameter. The second set of piston assemblies may be operatively coupled to the first crankshaft and comprise a third piston assembly having the first diameter and a fourth piston assembly having the second diameter. The second set of piston assemblies may be positioned on the crankshaft opposite the first set of piston assemblies such that the piston assemblies of the first set of piston assemblies and the piston assemblies of the second set of piston assemblies having the same diameter are aligned.

CROSS REFERENCE TO RELATED APPLICATIONS

This patent application claims the benefit of South African Provisionalpatent Application Serial No. 2018/04722 filed on Jul. 16, 2018 under 35U.S.C. § 119(e). South African Provisional Patent Application Serial No.2018/04722 is incorporated herein by reference in its entirety.

BACKGROUND

Compressed gas engines can be used as an alternative to internalcombustion engines to supply rotational mechanical energy to variousmachines. However, compressed gas engines typically require highlycompressed gas to match the energy content per unit mass that iscontained in a combustible fuel, such as gasoline. Further, theoperation of typical compressed gas engines can result in the rapiddecompression of the compressed gas, leading to a significant reductionin the temperature of the air and possible freezing of the compressedgas engine.

SUMMARY

Certain embodiments of the disclosed invention may include a compressedgas engine. The compressed gas engine may include a first crankshaft, afirst set of piston assemblies, a second set of piston assemblies, and afirst valve assembly. The first set of piston assemblies may be coupledto the first crankshaft and comprise a first piston assembly having afirst diameter and a second piston assembly having a second diameter.The second set of piston assemblies may be operatively coupled to thefirst crankshaft and comprise a third piston assembly having the firstdiameter and a fourth piston assembly having the second diameter. Thesecond set of piston assemblies may be positioned on the crankshaftopposite the first set of piston assemblies such that the pistonassemblies of the first set of piston assemblies and the pistonassemblies of the second set of piston assemblies having the samediameter are aligned. An open-side cavity of the first piston assemblymay be fluidly coupled to and receive compressed air from a compressedair source. A rod-side cavity of the second piston assembly may befluidly coupled to and receive partially expanded compressed air from arod-side cavity of the first piston assembly.

Certain embodiments of the disclosed invention may include of operatinga compressed gas engine. The method may include flowing compressed gasfrom a compressed gas source into a rod-side cavity of a first pistonassembly of a first set of piston assemblies operatively coupled to acrankshaft, the first piston assembly having a first diameter. Themethod may further include flowing compressed gas from the compressedgas source into an open-side cavity of a second piston assembly of asecond set of piston assemblies operatively coupled to the crankshaftand opposite the first set of piston assemblies, the second pistonassembly having the first diameter and being aligned with the firstpiston assembly. The method may also include forcing partially expandedcompressed gas to flow from an open-side cavity of the first pistonassembly into an open-side cavity of a third piston assembly of thefirst set of piston assemblies, the third piston assembly having asecond diameter. The method may further include forcing partiallyexpanded compressed gas to flow from a rod-side cavity of the secondpiston assembly into a rod-side cavity of a fourth piston assembly ofthe second set of piston assemblies, the fourth piston assembly havingthe second diameter and being aligned with the third piston assembly.

Other aspects of the invention will be apparent from the followingdescription and the appended claims.

BRIEF DESCRIPTION OF DRAWINGS

Embodiments of the compressed gas engine are described with reference tothe following figures. The same numbers are used throughout the figuresto reference like features and components. The features depicted in thefigures are not necessarily shown to scale. Certain features of theembodiments may be shown exaggerated in scale or in somewhat schematicform, and some details of elements may not be shown in the interest ofclarity and conciseness.

FIG. 1 is a schematic view of a compressed gas engine system accordingto one or more embodiments.

FIG. 2A is a schematic diagram of an engine module of FIG. 1 accordingto one or more embodiments.

FIG. 2B is a cross-sectional view of the engine module of FIG. 2A alongline B-B.

FIGS. 3A-3E are schematic diagrams illustrating the flow of compressedgas through the engine module of FIG. 2A according to one or moreembodiments.

FIG. 4 is a schematic diagram of an engine module according to one ormore embodiments.

FIG. 5A is a schematic diagram of the compressed gas engine of FIG. 1according to one or more embodiments.

FIG. 5B is a cross-sectional view of the compressed gas engine of FIG.5A along line B-B.

FIGS. 6A-6J are schematic diagrams illustrating the flow of compressedgas through an engine module according to one or more embodiments.

DETAILED DESCRIPTION

Specific embodiments of the invention will now be described in detailwith reference to the accompanying figures. In the following detaileddescription of the embodiments of the invention, numerous specificdetails are set forth in order to provide a more thorough understandingof the invention. However, it will be apparent to one of ordinary skillin the art that the invention may be practiced without these specificdetails. In other instances, well-known features have not been describedin detail to avoid unnecessarily complicating the description.

In the following description of FIGS. 1-6J, any component described withregard to a figure, in various embodiments of the invention, may beequivalent to one or more like-named components described with regard toany other figure. For brevity, descriptions of these components will notbe repeated with regard to each figure. Thus, each and every embodimentof the components of each figure is incorporated by reference andassumed to be optionally present within every other figure having one ormore like-named components. Additionally, in accordance with variousembodiments of the invention, any description of the components of afigure is to be interpreted as an optional embodiment, which may beimplemented in addition to, in conjunction with, or in place of theembodiments described with regard to a corresponding like-namedcomponent in any other figure.

Throughout the application, ordinal numbers (e.g., first, second, third,etc.) may be used as an adjective for an element (i.e., any noun in theapplication). The use of ordinal numbers is not to necessarily imply orcreate any particular ordering of the elements nor to limit any elementto being only a single element unless expressly disclosed, such as bythe use of the terms “before”, “after”, “single”, and other suchterminology. Rather, the use of ordinal numbers is to distinguishbetween the elements. By way of an example, a first element is distinctfrom a second element, and the first element may encompass more than oneelement and succeed (or precede) the second element in an ordering ofelements. Additionally, as used herein, the term “about,” when used inconjunction with a target value, means within a value 10% of the targetvalue.

The present disclosure provides a compressed gas engine system. Thecompressed gas engine system supplies rotational energy to rotatingcomponents, e.g., a generator, a gearbox, or a pump. The compressed gasengine system may also be used to supply rotational energy to othertypes of rotating components, e.g., boat propellers, electricalgenerators, and drive shafts for vehicles. However, the rotatingcomponents are not limited by the aforementioned examples.

FIG. 1 is a schematic diagram of a compressed gas engine system (100),according to one or more embodiments. Turning to FIG. 1, the compressedgas engine system (100) includes a compressed gas engine (102) fluidlycoupled to a compressed gas source (104) and a decompressed gascontainer (106), and operatively coupled to one or more rotatingcomponents (108).

The compressed gas engine system (100) also includes an enginemanagement system (110) that controls the operation of the compressedgas engine (102). The engine management system (110) controls a valveassembly (not shown) used to control the flow of compressed gas throughthe compressed gas engine (102). As discussed in more detail below, thevalve assembly may include spool valves or solenoid valves. However, theinvention is not thereby limited. In other embodiments, the valveassembly may include other types of valves, e.g., ball valves, rotaryvalves, or other types of flow control valves. However, the valves arenot limited by the aforementioned examples.

The compressed gas engine (102) decompresses the compressed gas receivedfrom the compressed gas source (104) in two or more stages, as discussedin more detail below, to provide the rotating component(s) (108) withrotational energy through a driveshaft (112) or similar structure. Thedecompression takes place in one or more engine modules (114, 116) thatare operatively coupled together to provide a single output to therotating component(s) (108). Although two engine modules (114, 116) areshown, this disclosure is not thereby limited. In other embodiments, thecompressed gas engine (102) may include one, three, or more enginemodules (114, 116).

After passing through the compressed gas engine (102), the decompressedgas typically remains at a pressure that is above ambient air pressureand is exhausted to the decompressed gas container (106) for storage.The gas stored in the decompressed gas container (106) can then berecompressed using less input energy than would otherwise be required tocompress the gas that powers the compressed gas engine system (100).Alternatively, the decompressed gas can be exhausted to the atmosphere.

The compressed gas engine (102) may decompress compressed air,compressed nitrogen, or any other compressed gas to provide therotational energy to the rotating component(s) (108). Additionally, thecompressed gas engine (100) may utilize a liquefied gas, e.g., liquidnitrogen. However, in such cases, the compressed gas engine system (100)includes an expansion device (not shown) that heats the vaporizingliquefied gas to ensure the resulting compressed gas is at anappropriate temperature for use in the compressed gas engine (100).

Turning now to FIG. 2A is an engine module 114 of FIG. 1 according toone or more embodiments. The engine module 114 includes multiple pistonassemblies (200A, 200B, 202A, 202B, 204A, 204B) that each include a rodassembly (206) that divides the internal cavity (208) of the pistonassembly (200A, 200B, 202A, 202B, 204A, 204B) into an open-side cavity(210) and a rod-side cavity (212). The rod assembly (206) includes a rod(214) that is coupled to a piston (215) through a pivot (not shown) andthat extends through the rod-side cavity (212) of the piston assembly(200A, 200B, 202A, 202B, 204A, 204B). The piston assemblies (200A, 200B,202A, 202B, 204A, 204B) also include an open-side port (216) in fluidcommunication with the open-side cavity (210) and a rod-side port (218)in fluid communication with the rod-side cavity (212).

As shown in FIG. 2A, the diameter of piston assemblies 204A and 204B isgreater than the diameter of piston assemblies 202A and 202B, which, inturn, is greater than the diameter of piston assemblies 200A and 200B.In at least one embodiment, the diameter of piston assemblies 202A and202B is within a range of 1.5 to 1.6 times the diameter of pistonassemblies 200A and 200B, and the diameter of piston assemblies 204A and204B is within a range of 1.5 to 1.6 times the diameter of pistonassemblies 202A and 202B. In other embodiments, the piston assemblies(200A, 200B, 202A, 202B, 204A, 204B) may have diameters of differentsizes and/or diameter ratios.

The rod assemblies (206) are coupled to a crankshaft (220) throughbearing assemblies (222) that allow the crankshaft (220) to rotatewithin the bearing assembly (222). The piston assemblies are arranged insets, i.e., piston assemblies 200A, 202A, and 204A, or piston assemblies200B, 202B, and 204B, which are positioned on either side of thecrankshaft (220) and aligned such that the piston assemblies (200A,200B, 202A, 202B, 204A, 204B) having the same diameter connect to thesame portion of the crankshaft (220). This configuration allows thepiston assemblies (200A, 200B, 202A, 202B, 204A, 204B) to rotate thecrankshaft (220) as the rod assemblies (206) extend and retract.

Additionally, as seen in FIG. 2B, the piston assemblies (200A, 200B,202A, 202B, 204A, 204B), are arranged along the same plane, e.g., thehorizontal plane shown in FIG. 2B. In other embodiments, the plane maybe vertical or any other orientation. The connection between thecrankshaft (220) and the bearing assemblies 220 of the respectiveadjacent piston assemblies (200A, 200B, 202A, 202B, 204A, 204B) of thesame piston assembly set, i.e., piston assemblies 200A, 202A, and 204A,or piston assemblies 200B, 202B, and 204B, are radially offset by 180degrees.

Referring back to FIG. 2A, the piston assemblies (200A, 200B, 202A,202B, 204A, 204B) and crankshaft (220) are supported by an engine frame(224) that maintains the relative positions of the piston assemblies(200A, 200B, 202A, 202B, 204A, 204B) and the crankshaft 220. The engineframe (224) includes multiple bearings (226), which support thecrankshaft (220) while allowing the crankshaft (220) to rotate withinthe engine frame (224). The engine module (114) also includes two spoolvalves (228A, 228B) that control the flow of air through the enginemodule (114), as described in more detail with reference to FIGS. 3A-3Eand 6A-6J.

Turning now to FIGS. 3A-3E, FIGS. 3A-3E are schematic diagramsillustrating the flow of compressed gas through the engine module (114)of FIG. 2A according to one or more embodiments. As shown in FIG. 3A,the spool valves (228A, 228B) are actuated to a first position to allowcompressed gas to flow from the compressed gas source (104) to therod-side port (218) of piston assembly 200A and the open-side port (216)of piston assembly 200B, respectively. This allows compressed gas toenter the rod-side cavity (212) of piston assembly 200A and theopen-side cavity (210) of piston assembly 200B, partially expanding thecompressed gas, retracting the rod assembly (206) of piston assembly200A, and extending the rod assembly (206) of piston assembly 200B. Themovement of the respective rod assemblies (206) rotates the crankshaft(220) to the position shown in FIG. 3A, while the pivot connections withthe piston (215) and bearing assemblies (222) allow the rod assemblies(206) to pivot as the rod assemblies (206) extend and retract.

The spool valves (228A, 228B) are then actuated to a second position toallow compressed gas to flow from the compressed gas source (104) to theopen-side port (216) of piston assembly 200A and the rod-side port (218)of piston assembly 200B, as shown in FIG. 3B. This allows compressed gasto enter the open-side cavity (210) of piston assembly 200A and therod-side cavity (212) of piston assembly 200B, extending the rodassembly (206) of piston assembly 200A and retracting the rod assembly(206) of piston assembly 200B.

The movement of the respective rod assemblies (206) also forces thepartially expanded compressed gas within the rod-side cavity (212) ofpiston 200A to pass through spool valve 228A and enter the rod-sidecavity (212) of piston 202A through the rod-side port (218), and thepartially expanded compressed gas within the open-side cavity (210) ofpiston 200B to pass through spool valve 228B and enter the open-sidecavity (210) of piston 202B through the open-side port (216). Theshifting of piston assemblies 200A, 200B, 202A, 202B to the positionsshown in FIG. 3B rotates the crankshaft (220) 180 degrees from theprevious position shown in FIG. 3A.

The spool valves (228A, 228B) are then actuated back to the firstposition, as shown in FIG. 3C, allowing compressed gas to again enterthe rod-side cavity (212) of piston assembly 200A and the open-sidecavity (210) of piston assembly 200B.

The compressed gas entering piston assembly 200A retracts the rodassembly (206) and forces the partially compressed gas within theopen-side cavity (210) of piston assembly 200A to pass through spoolvalve 228A and enter the open-side cavity (210) of piston 202A throughthe open-side port (216), extending the rod assembly (206) of pistonassembly 202A. The movement of the rod assembly (206) of piston assembly202A, in turn, forces the further expanded compressed gas within therod-side cavity (212) of piston 202A to pass through spool valve 228Aand enter the rod-side cavity (212) of piston 204A through the rod-sideport (218), retracting the rod assembly (206) of piston assembly 204A.

As this occurs, the compressed gas entering piston assembly 200B extendsthe rod assembly (206) and forces the partially compressed gas withinthe rod-side cavity (212) of piston assembly 200B to pass through spoolvalve 228B and enter the rod-side cavity (212) of piston 202A throughthe rod-side port (218), retracting the rod assembly (206) of pistonassembly 202B. The retraction of the rod assembly (206) of pistonassembly 202B forces the further expanded compressed gas within theopen-side cavity (210) of piston 202B to pass through spool valve 228Band enter the open-side cavity (210) of piston 204B through theopen-side port (216), extending the rod assembly (206) of pistonassembly 204B. The shifting of the piston assemblies (200A, 200B, 202A,202B, 204A, 204B) to the positions shown in FIG. 3C rotates thecrankshaft (220) 180 degrees from the previous position shown in FIG.3B.

The spool valves (228A, 228B) are then actuated to the second position,as shown in FIG. 3D, allowing compressed gas to again enter theopen-side cavity (210) of piston assembly 200A and the rod-side cavity(212) of piston assembly 200B.

The compressed gas entering piston assembly 200A extends the rodassembly (206) and forces the partially compressed gas within therod-side cavity (212) of piston assembly 200A to pass through spoolvalve 228A and enter the rod-side cavity (212) of piston 202A throughthe rod-side port (218), retracting the rod assembly (206) of pistonassembly 202A. In turn, the movement of the rod assembly (206) of pistonassembly 202A forces the further expanded compressed gas within theopen-side cavity (210) of piston 202A to pass through spool valve 228Aand enter the open-side cavity (210) of piston 204A through theopen-side port (216), extending the rod assembly (206) of pistonassembly 204A. The movement of the rod assembly (206) of piston assembly204A exhausts the decompressed gas within the rod-side cavity (212) ofpiston assembly 204A into the decompressed gas container (106).

As this occurs, the compressed gas entering piston assembly 200Bretracts the rod assembly (206) and forces the partially compressed gaswithin the open-side cavity (210) of piston assembly 200B to passthrough spool valve 228B and enter the open-side cavity (210) of piston202B through the open-side port (216), extending the rod assembly (206)of piston assembly 202B. In turn, the movement of the rod assembly (206)of piston assembly 202B forces the further expanded compressed gaswithin the rod-side cavity (212) of piston 202B to pass through spoolvalve 228B and enter the rod-side cavity (212) of piston 204B throughthe rod-side port (218), retracting the rod assembly (206) of pistonassembly 204B. The movement of the rod assembly (206) of piston assembly204B exhausts the decompressed gas within the open-side cavity (210) ofpiston assembly 204B into the decompressed gas container (106). Theshifting of the piston assemblies (200A, 200B, 202A, 202B, 204A, 204B)to the positions shown in FIG. 3D rotates the crankshaft (220) 180degrees from the previous position shown in FIG. 3C.

As previously noted, the decompressed gas entering the decompressed gascontainer (106) may still be at a pressure that is above ambientpressure, e.g., the gas may initially be at 200 psi, be decompressed to100 psi in piston assemblies 200A and 200B, be further decompressed to50 psi in piston assemblies 202A and 202B, and finally be decompressedto 25 psi in piston assemblies 204A and 204B. In other embodiments, thecompressed gas supply (104) may be at a pressure other than 200 psi, orthe piston assemblies (200A, 200B, 202A, 202B, 204A, 204B) maydecompress the compressed gas to different pressures.

The spool valves (228A, 228B) are then actuated to the first position,as shown in FIG. 3E, allowing compressed gas to again enter the rod-sidecavity (212) of piston assembly 200A and the open-side cavity (210) ofpiston assembly 200B.

The compressed gas entering piston assembly 200A retracts the rodassembly (206) and forces the partially compressed gas within theopen-side cavity (210) of piston assembly 200A to pass through spoolvalve 228A and enter the open-side cavity (210) of piston 202A throughthe open-side port (216), extending the rod assembly (206) of pistonassembly 202A. In turn, the movement of the rod assembly (206) of pistonassembly 202A forces the further expanded compressed gas within therod-side cavity (210) of piston 202A to pass through spool valve 228Aand enter the rod-side cavity (212) of piston 204A through the rod-sideport (218), retracting the rod assembly (206) of piston assembly 204A.The movement of the rod assembly (206) of piston assembly 204A exhauststhe decompressed gas within the open-side cavity (210) of pistonassembly 204A into the decompressed gas container (106).

As this occurs, the compressed gas entering piston assembly 200B extendsthe rod assembly (206) and forces the partially compressed gas withinthe rod-side cavity (212) of piston assembly 200B to pass through spoolvalve 228B and enter the rod-side cavity (212) of piston 202B throughthe rod-side port (218), retracting the rod assembly (206) of pistonassembly 202B. In turn, the movement of the rod assembly (206) of pistonassembly 202B forces the further expanded compressed gas within theopen-side cavity (210) of piston 202B to pass through spool valve 228Band enter the open-side cavity (210) of piston 204B through theopen-side port (216), extending the rod assembly (206) of pistonassembly 204B. The movement of the rod assembly (206) of piston assembly204B exhausts the decompressed gas within the rod-side cavity (212) ofpiston assembly 204B into the decompressed gas container (106). Theshifting of the piston assemblies (200A, 200B, 202A, 202B, 204A, 204B)to the positions shown in FIG. 3E rotates the crankshaft (220) 180degrees from the previous position shown in FIG. 3D.

Once the compressed gas engine (102) has reached the stage shown in FIG.3E, the spool valves (228A, 228B) alternate between the first and thesecond positions as shown in FIGS. 3D and 3E. The shifting of the pistonassemblies (200A, 200B, 202A, 202B, 204A, 204B) continues to rotate thecrankshaft (220) as the compressed gas from the compressed gas source isdecompressed in the compressed gas engine.

The use of multiple piston assemblies (200A, 200B, 202A, 202B, 204A,204B) allows the compressed gas to be gradually decompressed as ittravels through the compressed gas engine 114. This prevents a suddendrop in temperature of the gas that can lead to freezing of the pistonassemblies (200A, 200B, 202A, 202B, 204A, 204B). Additionally, thepiston assemblies (200A, 200B, 202A, 202B, 204A, 204B) are sized suchthat the force applied to the crankshaft (220) by the extension andretraction of the rod assemblies (206) is about equal for each pistonwithin the set of pistons. This allows additional energy to be extractedfrom the compressed gas as it is decompressed and increases the torquethat can be supplied by the crankshaft (220) to rotating components(108).

Turning now to FIG. 4, FIG. 4 is a schematic diagram of an engine module400 according to one or more embodiments. The engine module 400functions similarly to the engine module 114 described above withreference to FIGS. 3A-3E. However the spool valves (228A, 228B) havebeen replaced by solenoid valves (402, 404, 406, 408, 410, 410, 414,416, 418, 420, 422, 424). Specifically, each piston assembly (200A,200B, 202A, 202B, 204A, 204B) includes an open-side inlet solenoid valve(402, 404, 406), an open-side outlet solenoid valve (408, 410, 410), arod-side inlet solenoid valve (414, 416, 418) and a rod-side outletsolenoid valve (420, 422, 424).

As shown in FIG. 4, the piston assemblies (200A, 200B, 202A, 202B, 204A,204B) are directly connected to each other through inlet solenoid valves(404, 406, 416, 418) and outlet solenoid valves (408, 410, 420, 422).Additionally piston assemblies 200A and 200B are directly connected tothe compressed gas source (104) through inlet solenoid valves 402 andpiston assemblies 204A and 204B are directly connected to thedecompressed gas container (106) through outlet solenoid valves 424. Thesolenoid valves are actuated by an engine management system (110) toallow compressed gas into the respective cavities (210), (212) to allowthe piston assemblies (200A, 200B, 202A, 202B, 204A, 204B) to rotate thecrankshaft (220) as described above.

In one or more embodiments, inlet solenoid valves 404, 406, 416, 418 maybe fluidly connected to a junction having one side fluidly connected tothe respective outlet solenoid valve 408, 410, 420, 422 and the otherside fluidly connected to a second solenoid valve (426) that is fluidlyconnected to the compressed gas source (104). This configuration allowsthe engine management system (110) to boost the output torque of thecompressed gas engine (102) by supplementing the partially decompressedgas flowing into piston assemblies 202A, 202B, 204A, 204B withcompressed gas from the compressed gas source (104).

Turning now to FIG. 5A, FIG. 5A is a schematic diagram of the compressedgas engine (102) of FIG. 1 according to one or more embodiments. Theindividual engine modules (114, 116) of compressed gas engine (102) aresimilar to those described above with reference to FIGS. 2A-3E. However,crankshafts 220A and 220B of engine modules 114 and 116, respectively,are operatively coupled together to allow the crankshafts (220A, 220B)to rotate as a single unit. In some embodiments, the adjacent ends ofthe crankshafts (220A, 220B) are castellated to allow the crankshafts(220A, 220B) to rotate as one. In other embodiments, the crankshafts(220A, 220B) utilize mechanical fasters or other similar means tofunction as a single unit. In at least one embodiment, a singlecrankshaft (not shown) extends through both engine modules (114, 116).

The connection between the adjacent piston assemblies (200A, 200B, 202A,202B, 204A, 204B) of the same piston assembly set, i.e., pistonassemblies 200A, 202A, and 204A, or piston assemblies 200B, 202B, and204B, and the respective crankshaft (220A, 220B) are radially offset by180 degrees, as described above. However, as shown in FIG. 5B, theconnection between the crankshafts (220A, 220B) is such that theconnection between the piston assemblies (200A, 200B, 202A, 202B, 204A,204B) and the crankshaft (220A) of engine module 114 are radially offset90 degrees from the connections between piston assemblies (200A, 200B,202A, 202B, 204A, 204B) and the crankshaft (220B) of engine module 116.

The 90 degree offset between the crankshafts (220A, 220B) causes the rodassemblies (206) of one engine module (114, 116) to be extended andretracted, while the rod assemblies (206) of the other engine module(114, 116) are in a center position, as shown in FIG. 5A. Thisarrangement helps to prevent hydraulic lock-up of the compressed gasengine (102).

Turning now to FIGS. 6A-6J, FIGS. 6A-6J are schematic diagramsillustrating the flow of compressed gas through the compressed gasengine module (102) of FIG. 6A according to one or more embodiments. Asshown in FIG. 6A, the spool valves (600A, 600B) are actuated to a firstposition to allow compressed gas to flow from the compressed gas source(104) to the rod-side port (218) of piston assembly 200A and theopen-side port (216) of piston assembly 200B of engine module 114. Thisretracts the rod assembly (206A) of piston assembly 200A and extends therod assembly (206A) of piston assembly 200B. The movement of therespective rod assemblies (206A) rotates the crankshafts (220A, 220B) tothe position shown in FIG. 6A.

The spool valves (600A, 600B) are then actuated to the second position,as shown in FIG. 6B, allowing compressed gas to enter the rod-side port(218) of piston assembly 200A and the open-side port (216) of pistonassembly 200B of engine module 116. As this occurs, compressed gas flowsfrom the compressed gas source (104) to the open-side port (216) ofpiston assembly 200A and the rod-side port (218) of piston assembly 200Bof engine module 114. This extends the rod assembly (206A) of pistonassembly 200A and retracts the rod assembly (206) of piston assembly200B of engine module 114.

The flow of compressed gas into piston assemblies 200A and 200B ofengine module 114 also forces the partially expanded compressed gaswithin the rod-side cavity (212) of piston 200A to enter the rod-sideport (218), and the partially expanded compressed gas within theopen-side cavity (210) of piston 200B to enter the open-side cavity ofpiston 202B through the open-side port (216) of engine module 114,shifting the rod assemblies (206A) to a central position. The shiftingof the piston assemblies 200A, 200B, 202A, 202B of engine module 114 andpiston assemblies 200A and 200B of engine module 116 to the positionsshown in FIG. 6B rotates the crankshafts (220A, 220B) 90 degrees fromthe previous position shown in FIG. 6A.

The spool valves (600A, 600B) are then actuated to the third position,as shown in FIG. 6C, continuing the flow of compressed gas to theopen-side port (216) of piston assembly 200A and the rod-side port (218)of piston assembly 200B of engine module 114. As this occurs, compressedgas also flows from the compressed gas source (104) to the open-sideport (216) of piston assembly 200A and the rod-side port (218) of pistonassembly 200B of engine module 116.

The flow of compressed gas into piston assemblies 200A and 200B ofengine module 116 also forces the partially expanded compressed gaswithin the rod-side cavity (212) of piston assembly 200A to enter therod-side port (218) of piston assembly 202A, and the partially expandedcompressed gas within the open-side cavity (210) of piston assembly 200Bof engine module 116 to enter the open-side port (210) of pistonassembly 202B of engine module 114, shifting the rod assemblies (206B)to a central position. The shifting of piston assemblies 200A, 200B,202A, 202B of engine module 114 and piston assemblies 200A and 200B ofengine module 116 to the positions shown in FIG. 6C rotates thecrankshafts (220A, 220B) 90 degrees from the previous position shown inFIG. 6B.

The spool valves (600A, 600B) are then actuated to the fourth position,as shown in FIG. 6D, continuing the flow of compressed gas to theopen-side port (216) of piston assembly 200A and the rod-side port (218)of piston assembly 200B of engine module 116. As this occurs, compressedgas also flows from the compressed gas source (104) to the rod-side port(218) of piston assembly 200A and the open-side port (216) of pistonassembly 200B of engine module 114.

The flow of compressed gas into piston assemblies 200A and 200B ofengine module 114 also forces the partially expanded compressed gaswithin the open-side cavity (210) of piston assembly 200A of enginemodule 114 to enter the open-side port (216) of piston assembly 202A,and the partially expanded compressed gas within the rod-side cavity(212) of piston assembly 202A of engine module 114 to enter the rod-sideport (218) of piston assembly 204A of engine module 114.

At the same time, the partially expanded compressed gas within therod-side cavity (212) of piston assembly 200B of engine module 114 isforced to enter the rod-side port (212) of piston assembly 202B ofengine module 114, and the partially expanded compressed gas within theopen-side cavity (210) of piston assembly 202B of engine module 114 isforced to enter the open-side port (216) of piston assembly 204B. Theshifting of the piston assemblies (200A, 200B, 202A, 202B, 204A, 204B)of engine module 114 and piston assemblies 200A, 200B, 202A, and 202B ofengine module 116 to the positions shown in FIG. 6D rotates thecrankshafts (220A, 220B) 90 degrees from the previous position shown inFIG. 6C.

The spool valves (600A, 600B) are then actuated to back to the firstposition, as shown in FIG. 6E, continuing the flow of compressed gas tothe rod-side port (218) of piston assembly 200A and the open-side port(216) of piston assembly 200B of engine module 114. As this occurs,compressed gas also flows from the compressed gas source (104) to therod-side port (218) of piston assembly 200A and the open-side port (216)of piston assembly 200B of engine module 116.

The flow of compressed gas into piston assemblies 200A and 200B ofengine module 116 also forces the partially expanded compressed gaswithin the open-side cavity (210) of piston assembly 200A to enter theopen-side port (216) of piston assembly 202A, and the partially expandedcompressed gas within the rod-side cavity (212) of piston assembly 202Aof engine module 116 to enter the rod-side port (212) of piston assembly204A of engine module 116.

At the same time, the partially expanded compressed gas within therod-side cavity (212) of piston assembly 200B of engine module 116 isforced to enter the rod-side port (212) of piston assembly 202B, and thepartially expanded compressed gas within the open-side cavity (210) ofpiston assembly 202B of engine module 116 is forced to enter theopen-side port (216) of piston assembly 204B. The shifting of the pistonassemblies (200A, 200B, 202A, 202B, 204A, 204B) of the engine modules(114, 116) to the positions shown in FIG. 6E rotates the crankshafts(220A, 220B) 90 degrees from the previous position shown in FIG. 6D.

The spool valves (600A, 600B) are then actuated to second position, asshown in FIG. 6F, continuing the flow of compressed gas to the rod-sideport (218) of piston assembly 200A and the open-side port (216) ofpiston assembly 200B of engine module 116. As this occurs, compressedgas also flows from the compressed gas source (104) to the open-sideport (216) of piston assembly 200A and the rod-side port (218) of pistonassembly 200B of engine module 114.

This movement also forces the partially expanded compressed gas withinthe rod-side cavity (212) of piston assembly 200A of engine module 114is forced to enter the rod-side port (218) of piston assembly 202A, andthe partially expanded compressed gas within the open-side cavity (210)of piston assembly 202A of engine module 114 to enter the open-side port(216) of piston assembly 204A of engine module 114. The decompressed gaswithin the rod-side cavity (212) of piston assembly 204A of enginemodule 114 is then exhausted into the decompressed gas container (106).

At the same time, the partially expanded compressed gas within theopen-side cavity (210) of piston assembly 200B of engine module 114 isforced to enter the open-side port (216) of piston assembly 202B, andthe partially expanded compressed gas within the rod-side cavity (212)of piston assembly 202B of engine module 114 is forced to enter therod-side port (218) of piston assembly 204B. The decompressed gas withinthe open-side cavity (210) of piston assembly 204B of engine module 114is then exhausted into the decompressed gas container (106). Theshifting of the piston assemblies (200A, 200B, 202A, 202B, 204A, 204B)of the engine modules (114, 116) to the positions shown in FIG. 6Frotates the crankshafts (220A, 220B) 90 degrees from the previousposition shown in FIG. 6E.

The spool valves (600A, 600B) are then actuated to third position, asshown in FIG. 6G, continuing the flow of compressed gas to the open-sideport (218) of piston assembly 200A and the rod-side port (218) of pistonassembly 200B of engine module 114. As this occurs, compressed gas alsoflows from the compressed gas source (104) to the open-side port (216)of piston assembly 200A and the rod-side port (218) of piston assembly200B of engine module 116.

This movement also forces the partially expanded compressed gas withinthe rod-side cavity (218) of piston assembly 200A of engine module 116to enter the rod-side port (218) of piston assembly 202A, and thepartially expanded compressed gas within the open-side cavity (210) ofpiston assembly 202A of engine module 116 to enter the open-side port(210) of piston assembly 204A. The decompressed gas within the rod-sidecavity (212) of piston assembly 204A of engine module 116 is thenexhausted into the decompressed gas container (106).

At the same time, the partially expanded compressed gas within theopen-side cavity (210) of piston assembly 200B of engine module 116 isforced to enter the open-side port (216) of piston assembly 202B ofengine module 116, and the partially expanded compressed gas within therod-side cavity (212) of piston assembly 202B of engine module 116 isforced to enter the rod-side port (218) of piston assembly 204B. Thedecompressed gas within the open-side cavity (210) of piston assembly204B of engine module 116 is then exhausted into the decompressed gascontainer (106). The shifting of the piston assemblies (200A, 200B,202A, 202B, 204A, 204B) of the engine modules (114, 116) to thepositions shown in FIG. 6G rotates the crankshafts (220A, 220B) 90degrees from the previous position shown in FIG. 6F.

The spool valves (600A, 600B) are then actuated to fourth position, asshown in FIG. 6H, continuing the flow of compressed gas to the open-sideport (216) of piston assembly 200A and the rod-side port (218) of pistonassembly 200B of engine module 116. As this occurs, compressed gas alsoflows from the compressed gas source (104) to the rod-side port (218) ofpiston assembly 200A and the open-side port (216) of piston assembly200B of engine module 114.

This movement also forces the partially expanded compressed gas withinthe open-side cavity (210) of piston assembly 200A of engine module 114to enter the open-side port (216) of piston assembly 202A, and thepartially expanded compressed gas within the rod-side cavity (212) ofpiston assembly 202A of engine module 114 to enter the rod-side port(218) of piston assembly 204A. The decompressed gas within the open-sidecavity (210) of piston assembly 204A of engine module 114 is thenexhausted into the decompressed gas container (106).

At the same time, the partially expanded compressed gas within therod-side cavity (212) of piston assembly 200B of engine module 114 isforced to enter the rod-side port (218) of piston assembly 202B, and thepartially expanded compressed gas within the open-side cavity (210) ofpiston assembly 202B of engine module 114 is forced to enter theopen-side port (216) of piston assembly 204B. The decompressed gaswithin the rod-side cavity (212) of piston assembly 204B of enginemodule 114 is then exhausted into the decompressed gas container (106).The shifting of the piston assemblies (200A, 200B, 202A, 202B, 204A,204B) of the engine modules (114, 116) to the positions shown in FIG. 6Hrotates the crankshafts (220A, 220B) 90 degrees from the previousposition shown in FIG. 6G.

The spool valves (600A, 600B) are then actuated to fourth position, asshown in FIG. 6I, continuing the flow of compressed gas to the rod-sideport (218) of piston assembly 200A and the open-side port (216) ofpiston assembly 200B of engine module 114. As this occurs, compressedgas also flows from the compressed gas source (104) to the rod-side port(218) of piston assembly 200A and the open-side port (216) of pistonassembly 200B of engine module 116.

This movement also forces the partially expanded compressed gas withinthe open-side cavity (210) of piston assembly 200A of engine module 116to enter the open-side port (216) of piston assembly 202A, and thepartially expanded compressed gas within the rod-side cavity (212) ofpiston assembly 202A of engine module 116 to enter the rod-side port(218) of piston assembly 204A. The decompressed gas within the open-sidecavity (210) of piston assembly 204A of engine module 116 is thenexhausted into the decompressed gas container (106).

At the same time, the partially expanded compressed gas within therod-side cavity (212) of piston assembly 200B of engine module 116 isforced to enter the rod-side port (218) of piston assembly 202B ofengine module 116, and the partially expanded compressed gas within theopen-side cavity (210) of piston assembly 202B of engine module 116 isforced to enter the open-side port (216) of piston assembly 204B. Thedecompressed gas within the rod-side cavity (212) of piston assembly204B of engine module 116 is then exhausted into the decompressed gascontainer (106). The shifting of the piston assemblies (200A, 200B,202A, 202B, 204A, 204B) of the engine modules (114, 116) to thepositions shown in FIG. 6I rotates the crankshafts (220A, 220B) 90degrees from the previous position shown in FIG. 6H.

The spool valves (600A, 600B) are then actuated to fourth position, asshown in FIG. 6J, continuing the flow of compressed gas to the rod-sideport (218) of piston assembly 200A and the open-side port (216) ofpiston assembly 200B of engine module 116. As this occurs, compressedgas also flows from the compressed gas source (104) to the open-sideport (216) of piston assembly 200A and the rod-side port (218) of pistonassembly 200B of engine module 114.

This movement also forces the partially expanded compressed gas withinthe rod-side cavity (212) of piston assembly 200A of engine module 114to enter the rod-side port (218) of piston assembly 202A, and thepartially expanded compressed gas within the open-side cavity (210) ofpiston assembly 202A of engine module 114 to enter the open-side port(216) of piston assembly 204A of engine module 114. The decompressed gaswithin the rod-side cavity (212) of piston assembly 204A of enginemodule 114 is then exhausted into the decompressed gas container (106).

At the same time, the partially expanded compressed gas within theopen-side cavity (210) of piston assembly 200B of engine module 114 isforced to enter the open-side port (216) of piston assembly 202B ofengine module 114, and the partially expanded compressed gas within therod-side cavity (212) of piston assembly 202B of engine module 114 isforced to enter the rod-side port (218) of piston assembly 204B. Thedecompressed gas within the open-side cavity (210) of piston assembly204B of engine module 114 is then exhausted into the decompressed gascontainer (106). The shifting of the piston assemblies (200A, 200B,202A, 202B, 204A, 204B) of the engine modules (114, 116) to thepositions shown in FIG. 6J rotates the crankshafts (220A, 220B) 90degrees from the previous position shown in FIG. 6I.

Once the compressed gas engine (102) has reached the stage shown in FIG.6J, the spool valves (600A, 600B) alternate between the first, second,third, and fourth positions as shown in FIGS. 6G through 6J. Theshifting of the piston assemblies (200A, 200B, 202A, 202B, 204A, 204B)continues to rotate the crankshafts (220A, 220B) as the compressed gasfrom the compressed gas source is decompressed in the compressed gasengine.

One or more specific embodiments of compressed gas engine system havebeen described. In an effort to provide a concise description of theseembodiments, all features of an actual implementation may not bedescribed in the specification. It should be appreciated that in thedevelopment of any such actual implementation, as in any engineering ordesign project, numerous implementation-specific decisions must be madeto achieve the developers' specific goals, such as compliance withsystem-related and business-related constraints, which may vary from oneimplementation to another. Moreover, it should be appreciated that sucha development effort might be complex and time-consuming, but wouldnevertheless be a routine undertaking of design, fabrication, andmanufacture for those of ordinary skill having the benefit of thisdisclosure.

While the invention has been described with respect to a limited numberof embodiments, those skilled in the art, having benefit of thisdisclosure, will appreciate that other embodiments can be devised whichdo not depart from the scope of the invention as disclosed herein.Accordingly, the scope of the invention should be limited only by theattached claims.

What is claimed is:
 1. A compressed gas engine comprising: a firstengine module comprising: a first crankshaft; a first set of pistonassemblies operatively coupled to the first crankshaft and comprising afirst piston assembly having a first diameter and a second pistonassembly having a second diameter; a second set of piston assembliesoperatively coupled to the first crankshaft and comprising a thirdpiston assembly having the first diameter and a fourth piston assemblyhaving the second diameter, the second set of piston assembliespositioned on the crankshaft opposite the first set of piston assembliessuch that the piston assemblies of the first set of piston assembliesand the piston assemblies of the second set of piston assemblies havingthe same diameter are aligned; and a first valve assembly fluidlycoupled to the first set of pistons and the second set of pistons andconfigured to control a flow of compressed air through the first enginemodule; and wherein: an open-side cavity of the first piston assembly isfluidly coupled to and receives compressed air from a compressed airsource; and a rod-side cavity of the second piston assembly is fluidlycoupled to and receives partially expanded compressed air from arod-side cavity of the first piston assembly.
 2. The compressed airengine of claim 1, wherein the second diameter is larger than the firstdiameter.
 3. The compressed air engine of claim 1, wherein adjacentpiston assemblies within the same set of piston assemblies are connectedto the crankshaft at points that are radially offset from each other by180 degrees.
 4. The compressed air engine of claim 1, wherein the firstvalve assembly comprises at least one of plurality of spool valves or aplurality of solenoid valves.
 5. The compressed gas engine of claim 1,wherein: the rod-side cavity of the first piston assembly is fluidlycoupled to and receives compressed air from the compressed air source;and an open-side cavity of the second piston assembly is fluidly coupledto and receives partially expanded compressed air from the open-sidecavity of the first piston assembly.
 6. The compressed gas engine ofclaim 5, wherein: an open-side cavity of the third piston assembly isfluidly coupled to and receives compressed air from the compressed airsource; and a rod-side cavity of the fourth piston assembly is fluidlycoupled to and receives partially expanded compressed air from arod-side cavity of the third piston assembly.
 7. The compressed gasengine of claim 6, wherein: the rod-side cavity of the third pistonassembly is fluidly coupled to and receives compressed air from thecompressed air source; and an open-side cavity of the fourth pistonassembly is fluidly coupled to and receives partially expandedcompressed air from the open-side cavity of the third piston assembly.8. The compressed gas engine of claim 5, wherein: the rod-side cavity ofthe second piston assembly is fluidly coupled to and receives compressedair from the compressed air source; and the open-side cavity of thesecond piston assembly is fluidly coupled to and receives compressed airfrom the compressed air source.
 9. The compressed gas engine of claim 1,wherein: the first set of piston assemblies further comprises a fifthpiston assembly having a third diameter; and the second set of pistonassemblies comprises a sixth piston assembly having the third diameter.10. The compressed gas engine of claim 9, wherein a rod-side cavity ofthe fifth piston assembly is fluidly coupled to and receives furtherexpanded compressed air from the rod-side cavity of the second pistonassembly.
 11. The compressed air engine of claim 10, wherein therod-side cavity of the fifth piston assembly is fluidly coupled to andexhausts decompressed air to a decompressed air container.
 12. Thecompressed gas engine of claim 9, wherein an open-side cavity of thefifth piston assembly is fluidly coupled to and receives furtherexpanded compressed air from an open-side cavity of the second pistonassembly.
 13. The compressed air engine of claim 12, wherein theopen-side cavity of the fifth piston assembly is fluidly coupled to andexhausts decompressed air to a decompressed air container
 14. Thecompressed gas engine of claim 1, further comprising a second enginemodule comprising: a second crankshaft operatively coupled to the firstcrankshaft; and a third set of piston assemblies operatively coupled tothe second crankshaft and comprising a fifth piston assembly having thefirst diameter and a sixth piston assembly having the second diameter; afourth set of piston assemblies operatively coupled to the secondcrankshaft and comprising a seventh piston assembly having the firstdiameter and an eighth piston assembly having the second diameter, thefourth set of piston assemblies positioned on the crankshaft oppositethe third set of piston assemblies such that the piston assemblies ofthe third set of piston assemblies and the piston assemblies of thefourth set of piston assemblies having the same diameter are aligned;and a second valve assembly valve assembly fluidly coupled to the thirdset of pistons and the fourth set of pistons, and configured to controla flow of compressed air through the second engine module.
 15. Thecompressed gas engine of claim 14, wherein: adjacent piston assemblieswithin the same set of piston assemblies are connected to the respectivecrankshaft at points that are radially offset from each other by 180degrees; and the piston assemblies of the first and the second sets ofpiston assemblies are connected to the first crankshaft at points thatare radially offset by 90 degrees from connection points between thesecond crankshaft and the piston assemblies of the third and the fourthsets of piston assemblies.
 16. A method of operating a compressed gasengine, the method comprising: flowing compressed gas from a compressedgas source into a rod-side cavity of a first piston assembly of a firstset of piston assemblies operatively coupled to a crankshaft, the firstpiston assembly having a first diameter; flowing compressed gas from thecompressed gas source into an open-side cavity of a second pistonassembly of a second set of piston assemblies operatively coupled to thecrankshaft and opposite the first set of piston assemblies, the secondpiston assembly having the first diameter and being aligned with thefirst piston assembly; forcing partially expanded compressed gas to flowfrom an open-side cavity of the first piston assembly into an open-sidecavity of a third piston assembly of the first set of piston assemblies,the third piston assembly having a second diameter; and forcingpartially expanded compressed gas to flow from a rod-side cavity of thesecond piston assembly into a rod-side cavity of a fourth pistonassembly of the second set of piston assemblies, the fourth pistonassembly having the second diameter and being aligned with the thirdpiston assembly.
 17. The method of claim 16, wherein the second diameteris larger than the first diameter.
 18. The method of claim 16, furthercomprising: flowing compressed gas from the compressed gas source intothe open-side cavity of the first piston assembly; flowing compressedgas from the compressed gas source into the rod-side cavity of thesecond piston assembly; forcing partially expanded compressed gas toflow from the rod-side cavity of the first piston assembly into arod-side cavity of the third piston assembly; and forcing partiallyexpanded compressed gas to flow from the open-side cavity of the secondpiston assembly into an open-side cavity of the fourth piston assembly.19. The method of claim 18, wherein: the first set of piston assembliesfurther comprises a fifth piston assembly having a third diameter; thesecond set of piston assemblies further comprises a sixth pistonassembly having the third diameter and being aligned with the fifthpiston assembly; the third diameter is greater than the second diameter;the second diameter is greater than the first diameter; and the methodfurther comprises: forcing further expanded compressed gas to flow fromthe open-side cavity of the third piston assembly into an open-sidecavity of the fifth piston assembly; and forcing further expandedcompressed gas to flow from the rod-side cavity of the fourth pistonassembly into a rod-side cavity of the sixth piston assembly.
 20. Themethod of claim 19, further comprising: forcing further expandedcompressed gas to flow from the rod-side cavity of the third pistonassembly into a rod-side cavity of the fifth piston assembly; andforcing further expanded compressed gas to flow from the open-sidecavity of the fourth piston assembly into an open-side cavity of thesixth piston assembly.